gup.c 56.4 KB
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#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/spinlock.h>

#include <linux/mm.h>
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#include <linux/memremap.h>
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#include <linux/pagemap.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/swapops.h>

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#include <linux/sched/signal.h>
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#include <linux/rwsem.h>
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#include <linux/hugetlb.h>
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#include <linux/migrate.h>
#include <linux/mm_inline.h>
#include <linux/sched/mm.h>
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#include <asm/mmu_context.h>
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#include <asm/pgtable.h>
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#include <asm/tlbflush.h>
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#include "internal.h"

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struct follow_page_context {
	struct dev_pagemap *pgmap;
	unsigned int page_mask;
};

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static struct page *no_page_table(struct vm_area_struct *vma,
		unsigned int flags)
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{
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	/*
	 * When core dumping an enormous anonymous area that nobody
	 * has touched so far, we don't want to allocate unnecessary pages or
	 * page tables.  Return error instead of NULL to skip handle_mm_fault,
	 * then get_dump_page() will return NULL to leave a hole in the dump.
	 * But we can only make this optimization where a hole would surely
	 * be zero-filled if handle_mm_fault() actually did handle it.
	 */
	if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault))
		return ERR_PTR(-EFAULT);
	return NULL;
}
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static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
		pte_t *pte, unsigned int flags)
{
	/* No page to get reference */
	if (flags & FOLL_GET)
		return -EFAULT;

	if (flags & FOLL_TOUCH) {
		pte_t entry = *pte;

		if (flags & FOLL_WRITE)
			entry = pte_mkdirty(entry);
		entry = pte_mkyoung(entry);

		if (!pte_same(*pte, entry)) {
			set_pte_at(vma->vm_mm, address, pte, entry);
			update_mmu_cache(vma, address, pte);
		}
	}

	/* Proper page table entry exists, but no corresponding struct page */
	return -EEXIST;
}

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/*
 * FOLL_FORCE can write to even unwritable pte's, but only
 * after we've gone through a COW cycle and they are dirty.
 */
static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
{
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	return pte_write(pte) ||
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		((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
}

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static struct page *follow_page_pte(struct vm_area_struct *vma,
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		unsigned long address, pmd_t *pmd, unsigned int flags,
		struct dev_pagemap **pgmap)
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{
	struct mm_struct *mm = vma->vm_mm;
	struct page *page;
	spinlock_t *ptl;
	pte_t *ptep, pte;
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retry:
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	if (unlikely(pmd_bad(*pmd)))
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		return no_page_table(vma, flags);
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	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
	pte = *ptep;
	if (!pte_present(pte)) {
		swp_entry_t entry;
		/*
		 * KSM's break_ksm() relies upon recognizing a ksm page
		 * even while it is being migrated, so for that case we
		 * need migration_entry_wait().
		 */
		if (likely(!(flags & FOLL_MIGRATION)))
			goto no_page;
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		if (pte_none(pte))
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			goto no_page;
		entry = pte_to_swp_entry(pte);
		if (!is_migration_entry(entry))
			goto no_page;
		pte_unmap_unlock(ptep, ptl);
		migration_entry_wait(mm, pmd, address);
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		goto retry;
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	}
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	if ((flags & FOLL_NUMA) && pte_protnone(pte))
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		goto no_page;
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	if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
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		pte_unmap_unlock(ptep, ptl);
		return NULL;
	}
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	page = vm_normal_page(vma, address, pte);
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	if (!page && pte_devmap(pte) && (flags & FOLL_GET)) {
		/*
		 * Only return device mapping pages in the FOLL_GET case since
		 * they are only valid while holding the pgmap reference.
		 */
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		*pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap);
		if (*pgmap)
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			page = pte_page(pte);
		else
			goto no_page;
	} else if (unlikely(!page)) {
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		if (flags & FOLL_DUMP) {
			/* Avoid special (like zero) pages in core dumps */
			page = ERR_PTR(-EFAULT);
			goto out;
		}

		if (is_zero_pfn(pte_pfn(pte))) {
			page = pte_page(pte);
		} else {
			int ret;

			ret = follow_pfn_pte(vma, address, ptep, flags);
			page = ERR_PTR(ret);
			goto out;
		}
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	}

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	if (flags & FOLL_SPLIT && PageTransCompound(page)) {
		int ret;
		get_page(page);
		pte_unmap_unlock(ptep, ptl);
		lock_page(page);
		ret = split_huge_page(page);
		unlock_page(page);
		put_page(page);
		if (ret)
			return ERR_PTR(ret);
		goto retry;
	}

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	if (flags & FOLL_GET) {
		if (unlikely(!try_get_page(page))) {
			page = ERR_PTR(-ENOMEM);
			goto out;
		}
	}
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	if (flags & FOLL_TOUCH) {
		if ((flags & FOLL_WRITE) &&
		    !pte_dirty(pte) && !PageDirty(page))
			set_page_dirty(page);
		/*
		 * pte_mkyoung() would be more correct here, but atomic care
		 * is needed to avoid losing the dirty bit: it is easier to use
		 * mark_page_accessed().
		 */
		mark_page_accessed(page);
	}
E
Eric B Munson 已提交
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	if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
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		/* Do not mlock pte-mapped THP */
		if (PageTransCompound(page))
			goto out;

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		/*
		 * The preliminary mapping check is mainly to avoid the
		 * pointless overhead of lock_page on the ZERO_PAGE
		 * which might bounce very badly if there is contention.
		 *
		 * If the page is already locked, we don't need to
		 * handle it now - vmscan will handle it later if and
		 * when it attempts to reclaim the page.
		 */
		if (page->mapping && trylock_page(page)) {
			lru_add_drain();  /* push cached pages to LRU */
			/*
			 * Because we lock page here, and migration is
			 * blocked by the pte's page reference, and we
			 * know the page is still mapped, we don't even
			 * need to check for file-cache page truncation.
			 */
			mlock_vma_page(page);
			unlock_page(page);
		}
	}
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out:
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	pte_unmap_unlock(ptep, ptl);
	return page;
no_page:
	pte_unmap_unlock(ptep, ptl);
	if (!pte_none(pte))
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		return NULL;
	return no_page_table(vma, flags);
}

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static struct page *follow_pmd_mask(struct vm_area_struct *vma,
				    unsigned long address, pud_t *pudp,
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				    unsigned int flags,
				    struct follow_page_context *ctx)
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{
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	pmd_t *pmd, pmdval;
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	spinlock_t *ptl;
	struct page *page;
	struct mm_struct *mm = vma->vm_mm;

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	pmd = pmd_offset(pudp, address);
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	/*
	 * The READ_ONCE() will stabilize the pmdval in a register or
	 * on the stack so that it will stop changing under the code.
	 */
	pmdval = READ_ONCE(*pmd);
	if (pmd_none(pmdval))
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		return no_page_table(vma, flags);
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	if (pmd_huge(pmdval) && vma->vm_flags & VM_HUGETLB) {
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		page = follow_huge_pmd(mm, address, pmd, flags);
		if (page)
			return page;
		return no_page_table(vma, flags);
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	}
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	if (is_hugepd(__hugepd(pmd_val(pmdval)))) {
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		page = follow_huge_pd(vma, address,
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				      __hugepd(pmd_val(pmdval)), flags,
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				      PMD_SHIFT);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
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retry:
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	if (!pmd_present(pmdval)) {
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		if (likely(!(flags & FOLL_MIGRATION)))
			return no_page_table(vma, flags);
		VM_BUG_ON(thp_migration_supported() &&
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				  !is_pmd_migration_entry(pmdval));
		if (is_pmd_migration_entry(pmdval))
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			pmd_migration_entry_wait(mm, pmd);
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		pmdval = READ_ONCE(*pmd);
		/*
		 * MADV_DONTNEED may convert the pmd to null because
		 * mmap_sem is held in read mode
		 */
		if (pmd_none(pmdval))
			return no_page_table(vma, flags);
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		goto retry;
	}
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	if (pmd_devmap(pmdval)) {
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		ptl = pmd_lock(mm, pmd);
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		page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
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		spin_unlock(ptl);
		if (page)
			return page;
	}
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	if (likely(!pmd_trans_huge(pmdval)))
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		return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
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	if ((flags & FOLL_NUMA) && pmd_protnone(pmdval))
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		return no_page_table(vma, flags);

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retry_locked:
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	ptl = pmd_lock(mm, pmd);
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	if (unlikely(pmd_none(*pmd))) {
		spin_unlock(ptl);
		return no_page_table(vma, flags);
	}
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	if (unlikely(!pmd_present(*pmd))) {
		spin_unlock(ptl);
		if (likely(!(flags & FOLL_MIGRATION)))
			return no_page_table(vma, flags);
		pmd_migration_entry_wait(mm, pmd);
		goto retry_locked;
	}
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	if (unlikely(!pmd_trans_huge(*pmd))) {
		spin_unlock(ptl);
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		return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
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	}
	if (flags & FOLL_SPLIT) {
		int ret;
		page = pmd_page(*pmd);
		if (is_huge_zero_page(page)) {
			spin_unlock(ptl);
			ret = 0;
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			split_huge_pmd(vma, pmd, address);
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			if (pmd_trans_unstable(pmd))
				ret = -EBUSY;
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		} else {
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			if (unlikely(!try_get_page(page))) {
				spin_unlock(ptl);
				return ERR_PTR(-ENOMEM);
			}
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			spin_unlock(ptl);
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			lock_page(page);
			ret = split_huge_page(page);
			unlock_page(page);
			put_page(page);
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			if (pmd_none(*pmd))
				return no_page_table(vma, flags);
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		}

		return ret ? ERR_PTR(ret) :
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			follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
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	}
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	page = follow_trans_huge_pmd(vma, address, pmd, flags);
	spin_unlock(ptl);
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	ctx->page_mask = HPAGE_PMD_NR - 1;
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	return page;
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}

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static struct page *follow_pud_mask(struct vm_area_struct *vma,
				    unsigned long address, p4d_t *p4dp,
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				    unsigned int flags,
				    struct follow_page_context *ctx)
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{
	pud_t *pud;
	spinlock_t *ptl;
	struct page *page;
	struct mm_struct *mm = vma->vm_mm;

	pud = pud_offset(p4dp, address);
	if (pud_none(*pud))
		return no_page_table(vma, flags);
	if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
		page = follow_huge_pud(mm, address, pud, flags);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
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	if (is_hugepd(__hugepd(pud_val(*pud)))) {
		page = follow_huge_pd(vma, address,
				      __hugepd(pud_val(*pud)), flags,
				      PUD_SHIFT);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
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	if (pud_devmap(*pud)) {
		ptl = pud_lock(mm, pud);
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		page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap);
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		spin_unlock(ptl);
		if (page)
			return page;
	}
	if (unlikely(pud_bad(*pud)))
		return no_page_table(vma, flags);

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	return follow_pmd_mask(vma, address, pud, flags, ctx);
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}

static struct page *follow_p4d_mask(struct vm_area_struct *vma,
				    unsigned long address, pgd_t *pgdp,
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				    unsigned int flags,
				    struct follow_page_context *ctx)
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{
	p4d_t *p4d;
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	struct page *page;
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	p4d = p4d_offset(pgdp, address);
	if (p4d_none(*p4d))
		return no_page_table(vma, flags);
	BUILD_BUG_ON(p4d_huge(*p4d));
	if (unlikely(p4d_bad(*p4d)))
		return no_page_table(vma, flags);

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	if (is_hugepd(__hugepd(p4d_val(*p4d)))) {
		page = follow_huge_pd(vma, address,
				      __hugepd(p4d_val(*p4d)), flags,
				      P4D_SHIFT);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
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	return follow_pud_mask(vma, address, p4d, flags, ctx);
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}

/**
 * follow_page_mask - look up a page descriptor from a user-virtual address
 * @vma: vm_area_struct mapping @address
 * @address: virtual address to look up
 * @flags: flags modifying lookup behaviour
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 * @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
 *       pointer to output page_mask
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 *
 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
 *
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 * When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
 * the device's dev_pagemap metadata to avoid repeating expensive lookups.
 *
 * On output, the @ctx->page_mask is set according to the size of the page.
 *
 * Return: the mapped (struct page *), %NULL if no mapping exists, or
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 * an error pointer if there is a mapping to something not represented
 * by a page descriptor (see also vm_normal_page()).
 */
struct page *follow_page_mask(struct vm_area_struct *vma,
			      unsigned long address, unsigned int flags,
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			      struct follow_page_context *ctx)
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{
	pgd_t *pgd;
	struct page *page;
	struct mm_struct *mm = vma->vm_mm;

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	ctx->page_mask = 0;
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	/* make this handle hugepd */
	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
	if (!IS_ERR(page)) {
		BUG_ON(flags & FOLL_GET);
		return page;
	}

	pgd = pgd_offset(mm, address);

	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
		return no_page_table(vma, flags);

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	if (pgd_huge(*pgd)) {
		page = follow_huge_pgd(mm, address, pgd, flags);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
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	if (is_hugepd(__hugepd(pgd_val(*pgd)))) {
		page = follow_huge_pd(vma, address,
				      __hugepd(pgd_val(*pgd)), flags,
				      PGDIR_SHIFT);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
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	return follow_p4d_mask(vma, address, pgd, flags, ctx);
}

struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
			 unsigned int foll_flags)
{
	struct follow_page_context ctx = { NULL };
	struct page *page;

	page = follow_page_mask(vma, address, foll_flags, &ctx);
	if (ctx.pgmap)
		put_dev_pagemap(ctx.pgmap);
	return page;
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}

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static int get_gate_page(struct mm_struct *mm, unsigned long address,
		unsigned int gup_flags, struct vm_area_struct **vma,
		struct page **page)
{
	pgd_t *pgd;
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	p4d_t *p4d;
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	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
	int ret = -EFAULT;

	/* user gate pages are read-only */
	if (gup_flags & FOLL_WRITE)
		return -EFAULT;
	if (address > TASK_SIZE)
		pgd = pgd_offset_k(address);
	else
		pgd = pgd_offset_gate(mm, address);
	BUG_ON(pgd_none(*pgd));
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	p4d = p4d_offset(pgd, address);
	BUG_ON(p4d_none(*p4d));
	pud = pud_offset(p4d, address);
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	BUG_ON(pud_none(*pud));
	pmd = pmd_offset(pud, address);
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	if (!pmd_present(*pmd))
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		return -EFAULT;
	VM_BUG_ON(pmd_trans_huge(*pmd));
	pte = pte_offset_map(pmd, address);
	if (pte_none(*pte))
		goto unmap;
	*vma = get_gate_vma(mm);
	if (!page)
		goto out;
	*page = vm_normal_page(*vma, address, *pte);
	if (!*page) {
		if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
			goto unmap;
		*page = pte_page(*pte);
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		/*
		 * This should never happen (a device public page in the gate
		 * area).
		 */
		if (is_device_public_page(*page))
			goto unmap;
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	}
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	if (unlikely(!try_get_page(*page))) {
		ret = -ENOMEM;
		goto unmap;
	}
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out:
	ret = 0;
unmap:
	pte_unmap(pte);
	return ret;
}

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/*
 * mmap_sem must be held on entry.  If @nonblocking != NULL and
 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
 */
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static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
		unsigned long address, unsigned int *flags, int *nonblocking)
{
	unsigned int fault_flags = 0;
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	vm_fault_t ret;
531

E
Eric B Munson 已提交
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	/* mlock all present pages, but do not fault in new pages */
	if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
		return -ENOENT;
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	if (*flags & FOLL_WRITE)
		fault_flags |= FAULT_FLAG_WRITE;
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	if (*flags & FOLL_REMOTE)
		fault_flags |= FAULT_FLAG_REMOTE;
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	if (nonblocking)
		fault_flags |= FAULT_FLAG_ALLOW_RETRY;
	if (*flags & FOLL_NOWAIT)
		fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
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	if (*flags & FOLL_TRIED) {
		VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
		fault_flags |= FAULT_FLAG_TRIED;
	}
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548
	ret = handle_mm_fault(vma, address, fault_flags);
549
	if (ret & VM_FAULT_ERROR) {
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		int err = vm_fault_to_errno(ret, *flags);

		if (err)
			return err;
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		BUG();
	}

	if (tsk) {
		if (ret & VM_FAULT_MAJOR)
			tsk->maj_flt++;
		else
			tsk->min_flt++;
	}

	if (ret & VM_FAULT_RETRY) {
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		if (nonblocking && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
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			*nonblocking = 0;
		return -EBUSY;
	}

	/*
	 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
	 * necessary, even if maybe_mkwrite decided not to set pte_write. We
	 * can thus safely do subsequent page lookups as if they were reads.
	 * But only do so when looping for pte_write is futile: in some cases
	 * userspace may also be wanting to write to the gotten user page,
	 * which a read fault here might prevent (a readonly page might get
	 * reCOWed by userspace write).
	 */
	if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
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		*flags |= FOLL_COW;
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	return 0;
}

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static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
{
	vm_flags_t vm_flags = vma->vm_flags;
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	int write = (gup_flags & FOLL_WRITE);
	int foreign = (gup_flags & FOLL_REMOTE);
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	if (vm_flags & (VM_IO | VM_PFNMAP))
		return -EFAULT;

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	if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma))
		return -EFAULT;

596
	if (write) {
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		if (!(vm_flags & VM_WRITE)) {
			if (!(gup_flags & FOLL_FORCE))
				return -EFAULT;
			/*
			 * We used to let the write,force case do COW in a
			 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
			 * set a breakpoint in a read-only mapping of an
			 * executable, without corrupting the file (yet only
			 * when that file had been opened for writing!).
			 * Anon pages in shared mappings are surprising: now
			 * just reject it.
			 */
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			if (!is_cow_mapping(vm_flags))
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				return -EFAULT;
		}
	} else if (!(vm_flags & VM_READ)) {
		if (!(gup_flags & FOLL_FORCE))
			return -EFAULT;
		/*
		 * Is there actually any vma we can reach here which does not
		 * have VM_MAYREAD set?
		 */
		if (!(vm_flags & VM_MAYREAD))
			return -EFAULT;
	}
622 623 624 625 626
	/*
	 * gups are always data accesses, not instruction
	 * fetches, so execute=false here
	 */
	if (!arch_vma_access_permitted(vma, write, false, foreign))
627
		return -EFAULT;
628 629 630
	return 0;
}

631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650
/**
 * __get_user_pages() - pin user pages in memory
 * @tsk:	task_struct of target task
 * @mm:		mm_struct of target mm
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
 * @gup_flags:	flags modifying pin behaviour
 * @pages:	array that receives pointers to the pages pinned.
 *		Should be at least nr_pages long. Or NULL, if caller
 *		only intends to ensure the pages are faulted in.
 * @vmas:	array of pointers to vmas corresponding to each page.
 *		Or NULL if the caller does not require them.
 * @nonblocking: whether waiting for disk IO or mmap_sem contention
 *
 * Returns number of pages pinned. This may be fewer than the number
 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 * were pinned, returns -errno. Each page returned must be released
 * with a put_page() call when it is finished with. vmas will only
 * remain valid while mmap_sem is held.
 *
651
 * Must be called with mmap_sem held.  It may be released.  See below.
652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673
 *
 * __get_user_pages walks a process's page tables and takes a reference to
 * each struct page that each user address corresponds to at a given
 * instant. That is, it takes the page that would be accessed if a user
 * thread accesses the given user virtual address at that instant.
 *
 * This does not guarantee that the page exists in the user mappings when
 * __get_user_pages returns, and there may even be a completely different
 * page there in some cases (eg. if mmapped pagecache has been invalidated
 * and subsequently re faulted). However it does guarantee that the page
 * won't be freed completely. And mostly callers simply care that the page
 * contains data that was valid *at some point in time*. Typically, an IO
 * or similar operation cannot guarantee anything stronger anyway because
 * locks can't be held over the syscall boundary.
 *
 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
 * appropriate) must be called after the page is finished with, and
 * before put_page is called.
 *
 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
 * or mmap_sem contention, and if waiting is needed to pin all pages,
674 675 676 677 678 679 680 681
 * *@nonblocking will be set to 0.  Further, if @gup_flags does not
 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
 * this case.
 *
 * A caller using such a combination of @nonblocking and @gup_flags
 * must therefore hold the mmap_sem for reading only, and recognize
 * when it's been released.  Otherwise, it must be held for either
 * reading or writing and will not be released.
682 683 684 685 686
 *
 * In most cases, get_user_pages or get_user_pages_fast should be used
 * instead of __get_user_pages. __get_user_pages should be used only if
 * you need some special @gup_flags.
 */
L
Lorenzo Stoakes 已提交
687
static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
688 689 690 691
		unsigned long start, unsigned long nr_pages,
		unsigned int gup_flags, struct page **pages,
		struct vm_area_struct **vmas, int *nonblocking)
{
692
	long ret = 0, i = 0;
693
	struct vm_area_struct *vma = NULL;
694
	struct follow_page_context ctx = { NULL };
695 696 697 698 699 700 701 702 703 704 705 706 707 708 709

	if (!nr_pages)
		return 0;

	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));

	/*
	 * If FOLL_FORCE is set then do not force a full fault as the hinting
	 * fault information is unrelated to the reference behaviour of a task
	 * using the address space
	 */
	if (!(gup_flags & FOLL_FORCE))
		gup_flags |= FOLL_NUMA;

	do {
710 711 712 713 714 715 716 717 718 719 720 721
		struct page *page;
		unsigned int foll_flags = gup_flags;
		unsigned int page_increm;

		/* first iteration or cross vma bound */
		if (!vma || start >= vma->vm_end) {
			vma = find_extend_vma(mm, start);
			if (!vma && in_gate_area(mm, start)) {
				ret = get_gate_page(mm, start & PAGE_MASK,
						gup_flags, &vma,
						pages ? &pages[i] : NULL);
				if (ret)
722
					goto out;
723
				ctx.page_mask = 0;
724 725
				goto next_page;
			}
726

727 728 729 730
			if (!vma || check_vma_flags(vma, gup_flags)) {
				ret = -EFAULT;
				goto out;
			}
731 732 733
			if (is_vm_hugetlb_page(vma)) {
				i = follow_hugetlb_page(mm, vma, pages, vmas,
						&start, &nr_pages, i,
734
						gup_flags, nonblocking);
735
				continue;
736
			}
737 738 739 740 741 742
		}
retry:
		/*
		 * If we have a pending SIGKILL, don't keep faulting pages and
		 * potentially allocating memory.
		 */
743
		if (fatal_signal_pending(current)) {
744 745 746
			ret = -ERESTARTSYS;
			goto out;
		}
747
		cond_resched();
748 749

		page = follow_page_mask(vma, start, foll_flags, &ctx);
750 751 752 753 754 755
		if (!page) {
			ret = faultin_page(tsk, vma, start, &foll_flags,
					nonblocking);
			switch (ret) {
			case 0:
				goto retry;
756 757 758
			case -EBUSY:
				ret = 0;
				/* FALLTHRU */
759 760 761
			case -EFAULT:
			case -ENOMEM:
			case -EHWPOISON:
762
				goto out;
763 764
			case -ENOENT:
				goto next_page;
765
			}
766
			BUG();
767 768 769 770 771 772 773
		} else if (PTR_ERR(page) == -EEXIST) {
			/*
			 * Proper page table entry exists, but no corresponding
			 * struct page.
			 */
			goto next_page;
		} else if (IS_ERR(page)) {
774 775
			ret = PTR_ERR(page);
			goto out;
776
		}
777 778 779 780
		if (pages) {
			pages[i] = page;
			flush_anon_page(vma, page, start);
			flush_dcache_page(page);
781
			ctx.page_mask = 0;
782 783
		}
next_page:
784 785
		if (vmas) {
			vmas[i] = vma;
786
			ctx.page_mask = 0;
787
		}
788
		page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
789 790 791 792 793
		if (page_increm > nr_pages)
			page_increm = nr_pages;
		i += page_increm;
		start += page_increm * PAGE_SIZE;
		nr_pages -= page_increm;
794
	} while (nr_pages);
795 796 797 798
out:
	if (ctx.pgmap)
		put_dev_pagemap(ctx.pgmap);
	return i ? i : ret;
799 800
}

801 802
static bool vma_permits_fault(struct vm_area_struct *vma,
			      unsigned int fault_flags)
803
{
804 805
	bool write   = !!(fault_flags & FAULT_FLAG_WRITE);
	bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
806
	vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
807 808 809 810

	if (!(vm_flags & vma->vm_flags))
		return false;

811 812
	/*
	 * The architecture might have a hardware protection
813
	 * mechanism other than read/write that can deny access.
814 815 816
	 *
	 * gup always represents data access, not instruction
	 * fetches, so execute=false here:
817
	 */
818
	if (!arch_vma_access_permitted(vma, write, false, foreign))
819 820
		return false;

821 822 823
	return true;
}

824 825 826 827 828 829 830
/*
 * fixup_user_fault() - manually resolve a user page fault
 * @tsk:	the task_struct to use for page fault accounting, or
 *		NULL if faults are not to be recorded.
 * @mm:		mm_struct of target mm
 * @address:	user address
 * @fault_flags:flags to pass down to handle_mm_fault()
831 832
 * @unlocked:	did we unlock the mmap_sem while retrying, maybe NULL if caller
 *		does not allow retry
833 834 835 836 837 838 839 840 841 842 843
 *
 * This is meant to be called in the specific scenario where for locking reasons
 * we try to access user memory in atomic context (within a pagefault_disable()
 * section), this returns -EFAULT, and we want to resolve the user fault before
 * trying again.
 *
 * Typically this is meant to be used by the futex code.
 *
 * The main difference with get_user_pages() is that this function will
 * unconditionally call handle_mm_fault() which will in turn perform all the
 * necessary SW fixup of the dirty and young bits in the PTE, while
844
 * get_user_pages() only guarantees to update these in the struct page.
845 846 847 848 849 850
 *
 * This is important for some architectures where those bits also gate the
 * access permission to the page because they are maintained in software.  On
 * such architectures, gup() will not be enough to make a subsequent access
 * succeed.
 *
851 852
 * This function will not return with an unlocked mmap_sem. So it has not the
 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
853 854
 */
int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
855 856
		     unsigned long address, unsigned int fault_flags,
		     bool *unlocked)
857 858
{
	struct vm_area_struct *vma;
859
	vm_fault_t ret, major = 0;
860 861 862

	if (unlocked)
		fault_flags |= FAULT_FLAG_ALLOW_RETRY;
863

864
retry:
865 866 867 868
	vma = find_extend_vma(mm, address);
	if (!vma || address < vma->vm_start)
		return -EFAULT;

869
	if (!vma_permits_fault(vma, fault_flags))
870 871
		return -EFAULT;

872
	ret = handle_mm_fault(vma, address, fault_flags);
873
	major |= ret & VM_FAULT_MAJOR;
874
	if (ret & VM_FAULT_ERROR) {
875 876 877 878
		int err = vm_fault_to_errno(ret, 0);

		if (err)
			return err;
879 880
		BUG();
	}
881 882 883 884 885 886 887 888 889 890 891

	if (ret & VM_FAULT_RETRY) {
		down_read(&mm->mmap_sem);
		if (!(fault_flags & FAULT_FLAG_TRIED)) {
			*unlocked = true;
			fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
			fault_flags |= FAULT_FLAG_TRIED;
			goto retry;
		}
	}

892
	if (tsk) {
893
		if (major)
894 895 896 897 898 899
			tsk->maj_flt++;
		else
			tsk->min_flt++;
	}
	return 0;
}
900
EXPORT_SYMBOL_GPL(fixup_user_fault);
901

902 903 904 905 906 907
static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
						struct mm_struct *mm,
						unsigned long start,
						unsigned long nr_pages,
						struct page **pages,
						struct vm_area_struct **vmas,
908
						int *locked,
909
						unsigned int flags)
910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949
{
	long ret, pages_done;
	bool lock_dropped;

	if (locked) {
		/* if VM_FAULT_RETRY can be returned, vmas become invalid */
		BUG_ON(vmas);
		/* check caller initialized locked */
		BUG_ON(*locked != 1);
	}

	if (pages)
		flags |= FOLL_GET;

	pages_done = 0;
	lock_dropped = false;
	for (;;) {
		ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
				       vmas, locked);
		if (!locked)
			/* VM_FAULT_RETRY couldn't trigger, bypass */
			return ret;

		/* VM_FAULT_RETRY cannot return errors */
		if (!*locked) {
			BUG_ON(ret < 0);
			BUG_ON(ret >= nr_pages);
		}

		if (!pages)
			/* If it's a prefault don't insist harder */
			return ret;

		if (ret > 0) {
			nr_pages -= ret;
			pages_done += ret;
			if (!nr_pages)
				break;
		}
		if (*locked) {
950 951 952 953
			/*
			 * VM_FAULT_RETRY didn't trigger or it was a
			 * FOLL_NOWAIT.
			 */
954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984
			if (!pages_done)
				pages_done = ret;
			break;
		}
		/* VM_FAULT_RETRY triggered, so seek to the faulting offset */
		pages += ret;
		start += ret << PAGE_SHIFT;

		/*
		 * Repeat on the address that fired VM_FAULT_RETRY
		 * without FAULT_FLAG_ALLOW_RETRY but with
		 * FAULT_FLAG_TRIED.
		 */
		*locked = 1;
		lock_dropped = true;
		down_read(&mm->mmap_sem);
		ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
				       pages, NULL, NULL);
		if (ret != 1) {
			BUG_ON(ret > 1);
			if (!pages_done)
				pages_done = ret;
			break;
		}
		nr_pages--;
		pages_done++;
		if (!nr_pages)
			break;
		pages++;
		start += PAGE_SIZE;
	}
985
	if (lock_dropped && *locked) {
986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016
		/*
		 * We must let the caller know we temporarily dropped the lock
		 * and so the critical section protected by it was lost.
		 */
		up_read(&mm->mmap_sem);
		*locked = 0;
	}
	return pages_done;
}

/*
 * We can leverage the VM_FAULT_RETRY functionality in the page fault
 * paths better by using either get_user_pages_locked() or
 * get_user_pages_unlocked().
 *
 * get_user_pages_locked() is suitable to replace the form:
 *
 *      down_read(&mm->mmap_sem);
 *      do_something()
 *      get_user_pages(tsk, mm, ..., pages, NULL);
 *      up_read(&mm->mmap_sem);
 *
 *  to:
 *
 *      int locked = 1;
 *      down_read(&mm->mmap_sem);
 *      do_something()
 *      get_user_pages_locked(tsk, mm, ..., pages, &locked);
 *      if (locked)
 *          up_read(&mm->mmap_sem);
 */
1017
long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
1018
			   unsigned int gup_flags, struct page **pages,
1019 1020
			   int *locked)
{
1021 1022 1023 1024 1025 1026 1027 1028 1029
	/*
	 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
	 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
	 * vmas.  As there are no users of this flag in this call we simply
	 * disallow this option for now.
	 */
	if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
		return -EINVAL;

1030
	return __get_user_pages_locked(current, current->mm, start, nr_pages,
1031
				       pages, NULL, locked,
1032
				       gup_flags | FOLL_TOUCH);
1033
}
1034
EXPORT_SYMBOL(get_user_pages_locked);
1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047

/*
 * get_user_pages_unlocked() is suitable to replace the form:
 *
 *      down_read(&mm->mmap_sem);
 *      get_user_pages(tsk, mm, ..., pages, NULL);
 *      up_read(&mm->mmap_sem);
 *
 *  with:
 *
 *      get_user_pages_unlocked(tsk, mm, ..., pages);
 *
 * It is functionally equivalent to get_user_pages_fast so
1048 1049
 * get_user_pages_fast should be used instead if specific gup_flags
 * (e.g. FOLL_FORCE) are not required.
1050
 */
1051
long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
1052
			     struct page **pages, unsigned int gup_flags)
1053
{
1054 1055 1056 1057
	struct mm_struct *mm = current->mm;
	int locked = 1;
	long ret;

1058 1059 1060 1061 1062 1063 1064 1065 1066
	/*
	 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
	 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
	 * vmas.  As there are no users of this flag in this call we simply
	 * disallow this option for now.
	 */
	if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
		return -EINVAL;

1067 1068
	down_read(&mm->mmap_sem);
	ret = __get_user_pages_locked(current, mm, start, nr_pages, pages, NULL,
1069
				      &locked, gup_flags | FOLL_TOUCH);
1070 1071 1072
	if (locked)
		up_read(&mm->mmap_sem);
	return ret;
1073
}
1074
EXPORT_SYMBOL(get_user_pages_unlocked);
1075

1076
/*
1077
 * get_user_pages_remote() - pin user pages in memory
1078 1079 1080 1081 1082
 * @tsk:	the task_struct to use for page fault accounting, or
 *		NULL if faults are not to be recorded.
 * @mm:		mm_struct of target mm
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
1083
 * @gup_flags:	flags modifying lookup behaviour
1084 1085 1086 1087 1088
 * @pages:	array that receives pointers to the pages pinned.
 *		Should be at least nr_pages long. Or NULL, if caller
 *		only intends to ensure the pages are faulted in.
 * @vmas:	array of pointers to vmas corresponding to each page.
 *		Or NULL if the caller does not require them.
1089 1090 1091
 * @locked:	pointer to lock flag indicating whether lock is held and
 *		subsequently whether VM_FAULT_RETRY functionality can be
 *		utilised. Lock must initially be held.
1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114
 *
 * Returns number of pages pinned. This may be fewer than the number
 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 * were pinned, returns -errno. Each page returned must be released
 * with a put_page() call when it is finished with. vmas will only
 * remain valid while mmap_sem is held.
 *
 * Must be called with mmap_sem held for read or write.
 *
 * get_user_pages walks a process's page tables and takes a reference to
 * each struct page that each user address corresponds to at a given
 * instant. That is, it takes the page that would be accessed if a user
 * thread accesses the given user virtual address at that instant.
 *
 * This does not guarantee that the page exists in the user mappings when
 * get_user_pages returns, and there may even be a completely different
 * page there in some cases (eg. if mmapped pagecache has been invalidated
 * and subsequently re faulted). However it does guarantee that the page
 * won't be freed completely. And mostly callers simply care that the page
 * contains data that was valid *at some point in time*. Typically, an IO
 * or similar operation cannot guarantee anything stronger anyway because
 * locks can't be held over the syscall boundary.
 *
1115 1116 1117
 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
 * be called after the page is finished with, and before put_page is called.
1118 1119 1120 1121 1122 1123 1124 1125
 *
 * get_user_pages is typically used for fewer-copy IO operations, to get a
 * handle on the memory by some means other than accesses via the user virtual
 * addresses. The pages may be submitted for DMA to devices or accessed via
 * their kernel linear mapping (via the kmap APIs). Care should be taken to
 * use the correct cache flushing APIs.
 *
 * See also get_user_pages_fast, for performance critical applications.
1126 1127 1128 1129 1130
 *
 * get_user_pages should be phased out in favor of
 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
 * should use get_user_pages because it cannot pass
 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
1131
 */
1132 1133
long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
		unsigned long start, unsigned long nr_pages,
1134
		unsigned int gup_flags, struct page **pages,
1135
		struct vm_area_struct **vmas, int *locked)
1136
{
1137 1138 1139 1140 1141 1142 1143 1144 1145
	/*
	 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
	 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
	 * vmas.  As there are no users of this flag in this call we simply
	 * disallow this option for now.
	 */
	if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
		return -EINVAL;

1146
	return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
1147
				       locked,
1148
				       gup_flags | FOLL_TOUCH | FOLL_REMOTE);
1149 1150 1151
}
EXPORT_SYMBOL(get_user_pages_remote);

1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223
#if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA)
static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
{
	long i;
	struct vm_area_struct *vma_prev = NULL;

	for (i = 0; i < nr_pages; i++) {
		struct vm_area_struct *vma = vmas[i];

		if (vma == vma_prev)
			continue;

		vma_prev = vma;

		if (vma_is_fsdax(vma))
			return true;
	}
	return false;
}

#ifdef CONFIG_CMA
static struct page *new_non_cma_page(struct page *page, unsigned long private)
{
	/*
	 * We want to make sure we allocate the new page from the same node
	 * as the source page.
	 */
	int nid = page_to_nid(page);
	/*
	 * Trying to allocate a page for migration. Ignore allocation
	 * failure warnings. We don't force __GFP_THISNODE here because
	 * this node here is the node where we have CMA reservation and
	 * in some case these nodes will have really less non movable
	 * allocation memory.
	 */
	gfp_t gfp_mask = GFP_USER | __GFP_NOWARN;

	if (PageHighMem(page))
		gfp_mask |= __GFP_HIGHMEM;

#ifdef CONFIG_HUGETLB_PAGE
	if (PageHuge(page)) {
		struct hstate *h = page_hstate(page);
		/*
		 * We don't want to dequeue from the pool because pool pages will
		 * mostly be from the CMA region.
		 */
		return alloc_migrate_huge_page(h, gfp_mask, nid, NULL);
	}
#endif
	if (PageTransHuge(page)) {
		struct page *thp;
		/*
		 * ignore allocation failure warnings
		 */
		gfp_t thp_gfpmask = GFP_TRANSHUGE | __GFP_NOWARN;

		/*
		 * Remove the movable mask so that we don't allocate from
		 * CMA area again.
		 */
		thp_gfpmask &= ~__GFP_MOVABLE;
		thp = __alloc_pages_node(nid, thp_gfpmask, HPAGE_PMD_ORDER);
		if (!thp)
			return NULL;
		prep_transhuge_page(thp);
		return thp;
	}

	return __alloc_pages_node(nid, gfp_mask, 0);
}

1224 1225 1226 1227
static long check_and_migrate_cma_pages(struct task_struct *tsk,
					struct mm_struct *mm,
					unsigned long start,
					unsigned long nr_pages,
1228
					struct page **pages,
1229 1230
					struct vm_area_struct **vmas,
					unsigned int gup_flags)
1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285
{
	long i;
	bool drain_allow = true;
	bool migrate_allow = true;
	LIST_HEAD(cma_page_list);

check_again:
	for (i = 0; i < nr_pages; i++) {
		/*
		 * If we get a page from the CMA zone, since we are going to
		 * be pinning these entries, we might as well move them out
		 * of the CMA zone if possible.
		 */
		if (is_migrate_cma_page(pages[i])) {

			struct page *head = compound_head(pages[i]);

			if (PageHuge(head)) {
				isolate_huge_page(head, &cma_page_list);
			} else {
				if (!PageLRU(head) && drain_allow) {
					lru_add_drain_all();
					drain_allow = false;
				}

				if (!isolate_lru_page(head)) {
					list_add_tail(&head->lru, &cma_page_list);
					mod_node_page_state(page_pgdat(head),
							    NR_ISOLATED_ANON +
							    page_is_file_cache(head),
							    hpage_nr_pages(head));
				}
			}
		}
	}

	if (!list_empty(&cma_page_list)) {
		/*
		 * drop the above get_user_pages reference.
		 */
		for (i = 0; i < nr_pages; i++)
			put_page(pages[i]);

		if (migrate_pages(&cma_page_list, new_non_cma_page,
				  NULL, 0, MIGRATE_SYNC, MR_CONTIG_RANGE)) {
			/*
			 * some of the pages failed migration. Do get_user_pages
			 * without migration.
			 */
			migrate_allow = false;

			if (!list_empty(&cma_page_list))
				putback_movable_pages(&cma_page_list);
		}
		/*
1286 1287 1288
		 * We did migrate all the pages, Try to get the page references
		 * again migrating any new CMA pages which we failed to isolate
		 * earlier.
1289
		 */
1290 1291 1292 1293
		nr_pages = __get_user_pages_locked(tsk, mm, start, nr_pages,
						   pages, vmas, NULL,
						   gup_flags);

1294 1295 1296 1297 1298 1299 1300 1301 1302
		if ((nr_pages > 0) && migrate_allow) {
			drain_allow = true;
			goto check_again;
		}
	}

	return nr_pages;
}
#else
1303 1304 1305 1306 1307 1308 1309
static long check_and_migrate_cma_pages(struct task_struct *tsk,
					struct mm_struct *mm,
					unsigned long start,
					unsigned long nr_pages,
					struct page **pages,
					struct vm_area_struct **vmas,
					unsigned int gup_flags)
1310 1311 1312 1313 1314
{
	return nr_pages;
}
#endif

1315
/*
1316 1317
 * __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
 * allows us to process the FOLL_LONGTERM flag.
1318
 */
1319 1320 1321 1322 1323 1324 1325
static long __gup_longterm_locked(struct task_struct *tsk,
				  struct mm_struct *mm,
				  unsigned long start,
				  unsigned long nr_pages,
				  struct page **pages,
				  struct vm_area_struct **vmas,
				  unsigned int gup_flags)
1326
{
1327 1328
	struct vm_area_struct **vmas_tmp = vmas;
	unsigned long flags = 0;
1329 1330
	long rc, i;

1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342
	if (gup_flags & FOLL_LONGTERM) {
		if (!pages)
			return -EINVAL;

		if (!vmas_tmp) {
			vmas_tmp = kcalloc(nr_pages,
					   sizeof(struct vm_area_struct *),
					   GFP_KERNEL);
			if (!vmas_tmp)
				return -ENOMEM;
		}
		flags = memalloc_nocma_save();
1343 1344
	}

1345 1346
	rc = __get_user_pages_locked(tsk, mm, start, nr_pages, pages,
				     vmas_tmp, NULL, gup_flags);
1347

1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361
	if (gup_flags & FOLL_LONGTERM) {
		memalloc_nocma_restore(flags);
		if (rc < 0)
			goto out;

		if (check_dax_vmas(vmas_tmp, rc)) {
			for (i = 0; i < rc; i++)
				put_page(pages[i]);
			rc = -EOPNOTSUPP;
			goto out;
		}

		rc = check_and_migrate_cma_pages(tsk, mm, start, rc, pages,
						 vmas_tmp, gup_flags);
1362
	}
1363 1364

out:
1365 1366
	if (vmas_tmp != vmas)
		kfree(vmas_tmp);
1367 1368
	return rc;
}
1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397
#else /* !CONFIG_FS_DAX && !CONFIG_CMA */
static __always_inline long __gup_longterm_locked(struct task_struct *tsk,
						  struct mm_struct *mm,
						  unsigned long start,
						  unsigned long nr_pages,
						  struct page **pages,
						  struct vm_area_struct **vmas,
						  unsigned int flags)
{
	return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
				       NULL, flags);
}
#endif /* CONFIG_FS_DAX || CONFIG_CMA */

/*
 * This is the same as get_user_pages_remote(), just with a
 * less-flexible calling convention where we assume that the task
 * and mm being operated on are the current task's and don't allow
 * passing of a locked parameter.  We also obviously don't pass
 * FOLL_REMOTE in here.
 */
long get_user_pages(unsigned long start, unsigned long nr_pages,
		unsigned int gup_flags, struct page **pages,
		struct vm_area_struct **vmas)
{
	return __gup_longterm_locked(current, current->mm, start, nr_pages,
				     pages, vmas, gup_flags | FOLL_TOUCH);
}
EXPORT_SYMBOL(get_user_pages);
1398

1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430
/**
 * populate_vma_page_range() -  populate a range of pages in the vma.
 * @vma:   target vma
 * @start: start address
 * @end:   end address
 * @nonblocking:
 *
 * This takes care of mlocking the pages too if VM_LOCKED is set.
 *
 * return 0 on success, negative error code on error.
 *
 * vma->vm_mm->mmap_sem must be held.
 *
 * If @nonblocking is NULL, it may be held for read or write and will
 * be unperturbed.
 *
 * If @nonblocking is non-NULL, it must held for read only and may be
 * released.  If it's released, *@nonblocking will be set to 0.
 */
long populate_vma_page_range(struct vm_area_struct *vma,
		unsigned long start, unsigned long end, int *nonblocking)
{
	struct mm_struct *mm = vma->vm_mm;
	unsigned long nr_pages = (end - start) / PAGE_SIZE;
	int gup_flags;

	VM_BUG_ON(start & ~PAGE_MASK);
	VM_BUG_ON(end   & ~PAGE_MASK);
	VM_BUG_ON_VMA(start < vma->vm_start, vma);
	VM_BUG_ON_VMA(end   > vma->vm_end, vma);
	VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);

E
Eric B Munson 已提交
1431 1432 1433
	gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
	if (vma->vm_flags & VM_LOCKONFAULT)
		gup_flags &= ~FOLL_POPULATE;
1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516
	/*
	 * We want to touch writable mappings with a write fault in order
	 * to break COW, except for shared mappings because these don't COW
	 * and we would not want to dirty them for nothing.
	 */
	if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
		gup_flags |= FOLL_WRITE;

	/*
	 * We want mlock to succeed for regions that have any permissions
	 * other than PROT_NONE.
	 */
	if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
		gup_flags |= FOLL_FORCE;

	/*
	 * We made sure addr is within a VMA, so the following will
	 * not result in a stack expansion that recurses back here.
	 */
	return __get_user_pages(current, mm, start, nr_pages, gup_flags,
				NULL, NULL, nonblocking);
}

/*
 * __mm_populate - populate and/or mlock pages within a range of address space.
 *
 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
 * flags. VMAs must be already marked with the desired vm_flags, and
 * mmap_sem must not be held.
 */
int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
{
	struct mm_struct *mm = current->mm;
	unsigned long end, nstart, nend;
	struct vm_area_struct *vma = NULL;
	int locked = 0;
	long ret = 0;

	end = start + len;

	for (nstart = start; nstart < end; nstart = nend) {
		/*
		 * We want to fault in pages for [nstart; end) address range.
		 * Find first corresponding VMA.
		 */
		if (!locked) {
			locked = 1;
			down_read(&mm->mmap_sem);
			vma = find_vma(mm, nstart);
		} else if (nstart >= vma->vm_end)
			vma = vma->vm_next;
		if (!vma || vma->vm_start >= end)
			break;
		/*
		 * Set [nstart; nend) to intersection of desired address
		 * range with the first VMA. Also, skip undesirable VMA types.
		 */
		nend = min(end, vma->vm_end);
		if (vma->vm_flags & (VM_IO | VM_PFNMAP))
			continue;
		if (nstart < vma->vm_start)
			nstart = vma->vm_start;
		/*
		 * Now fault in a range of pages. populate_vma_page_range()
		 * double checks the vma flags, so that it won't mlock pages
		 * if the vma was already munlocked.
		 */
		ret = populate_vma_page_range(vma, nstart, nend, &locked);
		if (ret < 0) {
			if (ignore_errors) {
				ret = 0;
				continue;	/* continue at next VMA */
			}
			break;
		}
		nend = nstart + ret * PAGE_SIZE;
		ret = 0;
	}
	if (locked)
		up_read(&mm->mmap_sem);
	return ret;	/* 0 or negative error code */
}

1517 1518 1519 1520 1521
/**
 * get_dump_page() - pin user page in memory while writing it to core dump
 * @addr: user address
 *
 * Returns struct page pointer of user page pinned for dump,
1522
 * to be freed afterwards by put_page().
1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544
 *
 * Returns NULL on any kind of failure - a hole must then be inserted into
 * the corefile, to preserve alignment with its headers; and also returns
 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
 * allowing a hole to be left in the corefile to save diskspace.
 *
 * Called without mmap_sem, but after all other threads have been killed.
 */
#ifdef CONFIG_ELF_CORE
struct page *get_dump_page(unsigned long addr)
{
	struct vm_area_struct *vma;
	struct page *page;

	if (__get_user_pages(current, current->mm, addr, 1,
			     FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
			     NULL) < 1)
		return NULL;
	flush_cache_page(vma, addr, page_to_pfn(page));
	return page;
}
#endif /* CONFIG_ELF_CORE */
1545 1546

/*
1547
 * Generic Fast GUP
1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567
 *
 * get_user_pages_fast attempts to pin user pages by walking the page
 * tables directly and avoids taking locks. Thus the walker needs to be
 * protected from page table pages being freed from under it, and should
 * block any THP splits.
 *
 * One way to achieve this is to have the walker disable interrupts, and
 * rely on IPIs from the TLB flushing code blocking before the page table
 * pages are freed. This is unsuitable for architectures that do not need
 * to broadcast an IPI when invalidating TLBs.
 *
 * Another way to achieve this is to batch up page table containing pages
 * belonging to more than one mm_user, then rcu_sched a callback to free those
 * pages. Disabling interrupts will allow the fast_gup walker to both block
 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
 * (which is a relatively rare event). The code below adopts this strategy.
 *
 * Before activating this code, please be aware that the following assumptions
 * are currently made:
 *
1568 1569
 *  *) Either HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
 *  free pages containing page tables or TLB flushing requires IPI broadcast.
1570 1571 1572 1573 1574 1575 1576 1577 1578
 *
 *  *) ptes can be read atomically by the architecture.
 *
 *  *) access_ok is sufficient to validate userspace address ranges.
 *
 * The last two assumptions can be relaxed by the addition of helper functions.
 *
 * This code is based heavily on the PowerPC implementation by Nick Piggin.
 */
1579
#ifdef CONFIG_HAVE_GENERIC_GUP
1580

1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591
#ifndef gup_get_pte
/*
 * We assume that the PTE can be read atomically. If this is not the case for
 * your architecture, please provide the helper.
 */
static inline pte_t gup_get_pte(pte_t *ptep)
{
	return READ_ONCE(*ptep);
}
#endif

1592 1593 1594 1595 1596 1597 1598 1599 1600 1601
static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
{
	while ((*nr) - nr_start) {
		struct page *page = pages[--(*nr)];

		ClearPageReferenced(page);
		put_page(page);
	}
}

1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615
/*
 * Return the compund head page with ref appropriately incremented,
 * or NULL if that failed.
 */
static inline struct page *try_get_compound_head(struct page *page, int refs)
{
	struct page *head = compound_head(page);
	if (WARN_ON_ONCE(page_ref_count(head) < 0))
		return NULL;
	if (unlikely(!page_cache_add_speculative(head, refs)))
		return NULL;
	return head;
}

1616
#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
1617 1618 1619
static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
			 int write, struct page **pages, int *nr)
{
1620 1621
	struct dev_pagemap *pgmap = NULL;
	int nr_start = *nr, ret = 0;
1622 1623 1624 1625
	pte_t *ptep, *ptem;

	ptem = ptep = pte_offset_map(&pmd, addr);
	do {
1626
		pte_t pte = gup_get_pte(ptep);
1627
		struct page *head, *page;
1628 1629 1630

		/*
		 * Similar to the PMD case below, NUMA hinting must take slow
1631
		 * path using the pte_protnone check.
1632
		 */
1633 1634 1635 1636 1637 1638
		if (pte_protnone(pte))
			goto pte_unmap;

		if (!pte_access_permitted(pte, write))
			goto pte_unmap;

1639 1640 1641 1642 1643 1644 1645
		if (pte_devmap(pte)) {
			pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
			if (unlikely(!pgmap)) {
				undo_dev_pagemap(nr, nr_start, pages);
				goto pte_unmap;
			}
		} else if (pte_special(pte))
1646 1647 1648 1649 1650
			goto pte_unmap;

		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
		page = pte_page(pte);

1651 1652
		head = try_get_compound_head(page, 1);
		if (!head)
1653 1654 1655
			goto pte_unmap;

		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
1656
			put_page(head);
1657 1658 1659
			goto pte_unmap;
		}

1660
		VM_BUG_ON_PAGE(compound_head(page) != head, page);
1661 1662

		SetPageReferenced(page);
1663 1664 1665 1666 1667 1668 1669 1670
		pages[*nr] = page;
		(*nr)++;

	} while (ptep++, addr += PAGE_SIZE, addr != end);

	ret = 1;

pte_unmap:
1671 1672
	if (pgmap)
		put_dev_pagemap(pgmap);
1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691
	pte_unmap(ptem);
	return ret;
}
#else

/*
 * If we can't determine whether or not a pte is special, then fail immediately
 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
 * to be special.
 *
 * For a futex to be placed on a THP tail page, get_futex_key requires a
 * __get_user_pages_fast implementation that can pin pages. Thus it's still
 * useful to have gup_huge_pmd even if we can't operate on ptes.
 */
static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
			 int write, struct page **pages, int *nr)
{
	return 0;
}
1692
#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
1693

1694
#if defined(__HAVE_ARCH_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714
static int __gup_device_huge(unsigned long pfn, unsigned long addr,
		unsigned long end, struct page **pages, int *nr)
{
	int nr_start = *nr;
	struct dev_pagemap *pgmap = NULL;

	do {
		struct page *page = pfn_to_page(pfn);

		pgmap = get_dev_pagemap(pfn, pgmap);
		if (unlikely(!pgmap)) {
			undo_dev_pagemap(nr, nr_start, pages);
			return 0;
		}
		SetPageReferenced(page);
		pages[*nr] = page;
		get_page(page);
		(*nr)++;
		pfn++;
	} while (addr += PAGE_SIZE, addr != end);
1715 1716 1717

	if (pgmap)
		put_dev_pagemap(pgmap);
1718 1719 1720
	return 1;
}

1721
static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1722 1723 1724
		unsigned long end, struct page **pages, int *nr)
{
	unsigned long fault_pfn;
1725 1726 1727 1728 1729
	int nr_start = *nr;

	fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
	if (!__gup_device_huge(fault_pfn, addr, end, pages, nr))
		return 0;
1730

1731 1732 1733 1734 1735
	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
		undo_dev_pagemap(nr, nr_start, pages);
		return 0;
	}
	return 1;
1736 1737
}

1738
static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
1739 1740 1741
		unsigned long end, struct page **pages, int *nr)
{
	unsigned long fault_pfn;
1742 1743 1744 1745 1746
	int nr_start = *nr;

	fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
	if (!__gup_device_huge(fault_pfn, addr, end, pages, nr))
		return 0;
1747

1748 1749 1750 1751 1752
	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
		undo_dev_pagemap(nr, nr_start, pages);
		return 0;
	}
	return 1;
1753 1754
}
#else
1755
static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1756 1757 1758 1759 1760 1761
		unsigned long end, struct page **pages, int *nr)
{
	BUILD_BUG();
	return 0;
}

1762
static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
1763 1764 1765 1766 1767 1768 1769
		unsigned long end, struct page **pages, int *nr)
{
	BUILD_BUG();
	return 0;
}
#endif

1770 1771 1772
static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
		unsigned long end, int write, struct page **pages, int *nr)
{
1773
	struct page *head, *page;
1774 1775
	int refs;

1776
	if (!pmd_access_permitted(orig, write))
1777 1778
		return 0;

1779
	if (pmd_devmap(orig))
1780
		return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr);
1781

1782
	refs = 0;
1783
	page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
1784 1785 1786 1787 1788 1789 1790
	do {
		pages[*nr] = page;
		(*nr)++;
		page++;
		refs++;
	} while (addr += PAGE_SIZE, addr != end);

1791 1792
	head = try_get_compound_head(pmd_page(orig), refs);
	if (!head) {
1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803
		*nr -= refs;
		return 0;
	}

	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
		*nr -= refs;
		while (refs--)
			put_page(head);
		return 0;
	}

1804
	SetPageReferenced(head);
1805 1806 1807 1808 1809 1810
	return 1;
}

static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
		unsigned long end, int write, struct page **pages, int *nr)
{
1811
	struct page *head, *page;
1812 1813
	int refs;

1814
	if (!pud_access_permitted(orig, write))
1815 1816
		return 0;

1817
	if (pud_devmap(orig))
1818
		return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr);
1819

1820
	refs = 0;
1821
	page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
1822 1823 1824 1825 1826 1827 1828
	do {
		pages[*nr] = page;
		(*nr)++;
		page++;
		refs++;
	} while (addr += PAGE_SIZE, addr != end);

1829 1830
	head = try_get_compound_head(pud_page(orig), refs);
	if (!head) {
1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841
		*nr -= refs;
		return 0;
	}

	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
		*nr -= refs;
		while (refs--)
			put_page(head);
		return 0;
	}

1842
	SetPageReferenced(head);
1843 1844 1845
	return 1;
}

1846 1847 1848 1849 1850
static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
			unsigned long end, int write,
			struct page **pages, int *nr)
{
	int refs;
1851
	struct page *head, *page;
1852

1853
	if (!pgd_access_permitted(orig, write))
1854 1855
		return 0;

1856
	BUILD_BUG_ON(pgd_devmap(orig));
1857
	refs = 0;
1858
	page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
1859 1860 1861 1862 1863 1864 1865
	do {
		pages[*nr] = page;
		(*nr)++;
		page++;
		refs++;
	} while (addr += PAGE_SIZE, addr != end);

1866 1867
	head = try_get_compound_head(pgd_page(orig), refs);
	if (!head) {
1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878
		*nr -= refs;
		return 0;
	}

	if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
		*nr -= refs;
		while (refs--)
			put_page(head);
		return 0;
	}

1879
	SetPageReferenced(head);
1880 1881 1882
	return 1;
}

1883 1884 1885 1886 1887 1888 1889 1890
static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
		int write, struct page **pages, int *nr)
{
	unsigned long next;
	pmd_t *pmdp;

	pmdp = pmd_offset(&pud, addr);
	do {
1891
		pmd_t pmd = READ_ONCE(*pmdp);
1892 1893

		next = pmd_addr_end(addr, end);
1894
		if (!pmd_present(pmd))
1895 1896
			return 0;

Y
Yu Zhao 已提交
1897 1898
		if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
			     pmd_devmap(pmd))) {
1899 1900 1901 1902 1903
			/*
			 * NUMA hinting faults need to be handled in the GUP
			 * slowpath for accounting purposes and so that they
			 * can be serialised against THP migration.
			 */
1904
			if (pmd_protnone(pmd))
1905 1906 1907 1908 1909 1910
				return 0;

			if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
				pages, nr))
				return 0;

1911 1912 1913 1914 1915 1916 1917 1918
		} else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
			/*
			 * architecture have different format for hugetlbfs
			 * pmd format and THP pmd format
			 */
			if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
					 PMD_SHIFT, next, write, pages, nr))
				return 0;
1919
		} else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
1920
			return 0;
1921 1922 1923 1924 1925
	} while (pmdp++, addr = next, addr != end);

	return 1;
}

1926
static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
1927
			 int write, struct page **pages, int *nr)
1928 1929 1930 1931
{
	unsigned long next;
	pud_t *pudp;

1932
	pudp = pud_offset(&p4d, addr);
1933
	do {
1934
		pud_t pud = READ_ONCE(*pudp);
1935 1936 1937 1938

		next = pud_addr_end(addr, end);
		if (pud_none(pud))
			return 0;
1939
		if (unlikely(pud_huge(pud))) {
1940
			if (!gup_huge_pud(pud, pudp, addr, next, write,
1941 1942 1943 1944 1945
					  pages, nr))
				return 0;
		} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
			if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
					 PUD_SHIFT, next, write, pages, nr))
1946 1947 1948 1949 1950 1951 1952 1953
				return 0;
		} else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
			return 0;
	} while (pudp++, addr = next, addr != end);

	return 1;
}

1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971
static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
			 int write, struct page **pages, int *nr)
{
	unsigned long next;
	p4d_t *p4dp;

	p4dp = p4d_offset(&pgd, addr);
	do {
		p4d_t p4d = READ_ONCE(*p4dp);

		next = p4d_addr_end(addr, end);
		if (p4d_none(p4d))
			return 0;
		BUILD_BUG_ON(p4d_huge(p4d));
		if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
			if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
					 P4D_SHIFT, next, write, pages, nr))
				return 0;
1972
		} else if (!gup_pud_range(p4d, addr, next, write, pages, nr))
1973 1974 1975 1976 1977 1978
			return 0;
	} while (p4dp++, addr = next, addr != end);

	return 1;
}

1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
static void gup_pgd_range(unsigned long addr, unsigned long end,
		int write, struct page **pages, int *nr)
{
	unsigned long next;
	pgd_t *pgdp;

	pgdp = pgd_offset(current->mm, addr);
	do {
		pgd_t pgd = READ_ONCE(*pgdp);

		next = pgd_addr_end(addr, end);
		if (pgd_none(pgd))
			return;
		if (unlikely(pgd_huge(pgd))) {
			if (!gup_huge_pgd(pgd, pgdp, addr, next, write,
					  pages, nr))
				return;
		} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
			if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
					 PGDIR_SHIFT, next, write, pages, nr))
				return;
		} else if (!gup_p4d_range(pgd, addr, next, write, pages, nr))
			return;
	} while (pgdp++, addr = next, addr != end);
}

#ifndef gup_fast_permitted
/*
 * Check if it's allowed to use __get_user_pages_fast() for the range, or
 * we need to fall back to the slow version:
 */
2010
bool gup_fast_permitted(unsigned long start, int nr_pages)
2011 2012 2013 2014 2015 2016 2017 2018 2019
{
	unsigned long len, end;

	len = (unsigned long) nr_pages << PAGE_SHIFT;
	end = start + len;
	return end >= start;
}
#endif

2020 2021
/*
 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
2022 2023 2024
 * the regular GUP.
 * Note a difference with get_user_pages_fast: this always returns the
 * number of pages pinned, 0 if no pages were pinned.
2025 2026 2027 2028
 */
int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
			  struct page **pages)
{
2029
	unsigned long len, end;
2030
	unsigned long flags;
2031 2032 2033 2034 2035 2036
	int nr = 0;

	start &= PAGE_MASK;
	len = (unsigned long) nr_pages << PAGE_SHIFT;
	end = start + len;

2037
	if (unlikely(!access_ok((void __user *)start, len)))
2038 2039 2040 2041 2042 2043 2044
		return 0;

	/*
	 * Disable interrupts.  We use the nested form as we can already have
	 * interrupts disabled by get_futex_key.
	 *
	 * With interrupts disabled, we block page table pages from being
2045 2046
	 * freed from under us. See struct mmu_table_batch comments in
	 * include/asm-generic/tlb.h for more details.
2047 2048 2049 2050 2051
	 *
	 * We do not adopt an rcu_read_lock(.) here as we also want to
	 * block IPIs that come from THPs splitting.
	 */

2052
	if (gup_fast_permitted(start, nr_pages)) {
2053
		local_irq_save(flags);
2054
		gup_pgd_range(start, end, write, pages, &nr);
2055 2056
		local_irq_restore(flags);
	}
2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079

	return nr;
}

/**
 * get_user_pages_fast() - pin user pages in memory
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
 * @write:	whether pages will be written to
 * @pages:	array that receives pointers to the pages pinned.
 *		Should be at least nr_pages long.
 *
 * Attempt to pin user pages in memory without taking mm->mmap_sem.
 * If not successful, it will fall back to taking the lock and
 * calling get_user_pages().
 *
 * Returns number of pages pinned. This may be fewer than the number
 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 * were pinned, returns -errno.
 */
int get_user_pages_fast(unsigned long start, int nr_pages, int write,
			struct page **pages)
{
2080
	unsigned long addr, len, end;
2081
	int nr = 0, ret = 0;
2082 2083

	start &= PAGE_MASK;
2084 2085 2086 2087
	addr = start;
	len = (unsigned long) nr_pages << PAGE_SHIFT;
	end = start + len;

2088 2089 2090
	if (nr_pages <= 0)
		return 0;

2091
	if (unlikely(!access_ok((void __user *)start, len)))
2092
		return -EFAULT;
2093

2094
	if (gup_fast_permitted(start, nr_pages)) {
2095 2096 2097
		local_irq_disable();
		gup_pgd_range(addr, end, write, pages, &nr);
		local_irq_enable();
2098 2099
		ret = nr;
	}
2100 2101 2102 2103 2104 2105

	if (nr < nr_pages) {
		/* Try to get the remaining pages with get_user_pages */
		start += nr << PAGE_SHIFT;
		pages += nr;

2106 2107
		ret = get_user_pages_unlocked(start, nr_pages - nr, pages,
				write ? FOLL_WRITE : 0);
2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120

		/* Have to be a bit careful with return values */
		if (nr > 0) {
			if (ret < 0)
				ret = nr;
			else
				ret += nr;
		}
	}

	return ret;
}

2121
#endif /* CONFIG_HAVE_GENERIC_GUP */